Transformer core and lamination therefor



Aug. 17, 1965 R. c. BAENzlGER ETAL 3,201,731

TRANSFORMER CORE AND LAMINATION THEREFOR Filed Nov. 27, 1962 65 647[m1101121 lam/0N *1., l l 44 j ZH @#5246150 Y 60 fb 1 H6474@ HHH f 29:|smrm-n lmroncl mmm al 5TAT|O-A umm u y@ @i [l M1111 H W1 m Wm [i [I@01] 721] 96 I L I y.

' INVENTORS, -befZCQ/zg gen A BYJOmj/iwger,

United States Patent O .li Ja.

3,201,731 TRANSFRMER CURE AND LAMINATEN ,THEREFGR .Robert C. Baenziger,Northbrook, and Sohn F. Rieger,

Wilmette, Ill., assigner-s to Electro-Natie Steel, Inc., .Schiller Park,Ill., a corporation of Illinois Filed Nov. 27, 1962, Ser. No. 240,276

2 Claims. (Cl. 336-212) The present invention relates itself toelectromagnetic induction apparatus, and more particularly to the formand manufacture of laminations for stacked transformers.

Every electromagnetic induction device is a flux generator and fromevery flux generator there is a certain beam deflection system. With thecurrent trend rtoward stressed dellection systems; the problem createdby flux is critical. It is to this general problem of preventing fluxleakage from transformer cores in the most effective Vand leastexpensive way that the present invention directs itself.

There are several Ways of controlling the leakage flux so as to avoidstray flux fields, one of which is to decrease the flux density in atransformer by increasing ,the core size. But, of course, this iscontrary .to the trend toward compactness and results only in a largerand more expen- Copper bands around the core tend to containthe fluxlines and reduce liux leakage and orientation of the transformer core onthe television chassis may also avoid stray flux fields butthesesolutions are limited in their effectiveness. One of the bestmethods that has been devised for solving'this problem of flux leakageis to completely enclose the transformer in a shield or can whereby allthe flux lines are contained Within the can. Although effective, thismanner of solution is expensive.

It has now become a practice to make power transformers in radio andtelevisionV circuits of stacked interleaved U and I laminations, whichtransformer is enclosed construction is expensive not only in thatitincludes the extra element of a can but also in that in making theinterleaved stacking it is necessary that the laminations beindividually'handled. Thus, although the resulting core type transformeris effective for reducing component size, it is considerably moreexpensive in material cost and in labor expense than is preferred fortelevision power transformer usage.

A general object of the present invention is to provide a new and'improved stacked lamination transformer core structure and laminationtherefor permitting of relatively inexpensive construction, ease ofassembly and minimum flux leakage.

A further object of the invention is to provide a lamination formadapted for use in a stacked lamination transformer core structureandwhich lamination is of a configuration so as to permit the stamping outof the metal strip with no substantial loss in material.

An additional object of the invention is to provide a method of makingthe novel lamination in accordance with the invention from a singlestrip of magnetically permeable metal and without the wasting of anysignificant amount of metal material.

A specific object of the invention is to provide a modified U shapedlamination includingtwo leg portions joined by a bight portion whereinthe legs may be of any length 3,2@L73l Patented Aug. y17', 1965 withinthe limitation that one leg is shorter than the other leg byapproximately the width of the bight portion. Accordingly, in stampingout this lamination from a rectangular Vportion of a metallic strip itis possible to interdigiytate the positions of the modified U blanks sothat in the punching of one blank from the strip, that which is left isan identical modified U blank. Laminations so formed are stacked intotwo complementary stacks, windings, inserted over the legs of one stackand the two stacks butted, thereby to forma butted U-U core typetransformer for Vwhich the distributed windings overlie the buttedjoints thereby reducing of flux leakage and substantially avoiding strayflux lines. It is obvious that a shell type can be formed from two coretype structures with the same advantages in caseof assembly andreduction of flux leakage.

Further objects and features ofthe invention pertain to the particulararrangement and structure whereby the above identified and other objectsof the invention are attained. The invention, its structure, its methodof manufacture and its arrangement for use will be better understood byreference to the following specification and drawings forming a partthereof, wherein:

FIGURE l is a View in ,perspective of a modified U lamination inaccordance with the present invention;

FIGURE 2 is a perspective view of two complementary stacks oflaminations as shown in FIGURE 1 split and arranged for butting so as toform a core type transformer;

FIGURE 3A is an elevational View of a core type transformer made fromthe laminations of FIGURE l;

VFIGURE 3B is an elevational view of a shell type transformer made fromthe laminations of FIGURE l;

FIGURES 4A and 4B illustrate two methods for stamping blanks inaccordance with the invention from a strip of magnetically permeablematerial; and,

FGURE 5 illustrates another method of stamping blanks in accordance withthe invention from a strip of magnetically permeable material.

Referring first to FIGURE 1, there is shown therein in perspective viewa lamination 10 made up of integrally formed leg portions 12 and l11iand a lbight portion '1.6. .The laminati-on 1G is a blank stamped from athin sheet of magnetically permeable metallic material for which themagnetic grain may or may not be oriented depending upon the costrequirements and the magnetic circuit standards to be met. The leg l2 isIof a length l and the bight portion 16 is of a width a. Preferentiallythen the leg portion 14 is of a length l-a, with the legs |14 and y12each being of a width b. The bight portion lo is of a length 3b, lasshown. Where grain oriented material is employed it may be that it willbe preferred to compensate for the difference between ingrain andcross-grain permeability by making the crossgrain `dimen-sion largerthan the in-grain dimension. For example, if the lamination 10 were ablank of material grain oriented in the direction indicated by the arrow18 and if it were desired to compensate for the difference between themagnetic permeability of the in-grain and cross-grain areas, thedimension a would be greater than the dimension b by an amountsubstantially in proportion to the ldifference between in-grain andcrossgrain permeability of the magnetic material.

The `manner in which the laminati-ons 1li illustrated in FIGURE 1 arestackedin order to form a butted core is illustrated in FIGURE 2.Therein the laminations 1li are arranged in la `first stack 22 and in asecond stack 24 wherein the stack 22 provides a butting face 26associated with the leg portions 12 and a butting face 28 associatedwith the leg portions 14, and the stack 24 provides a butting face 36associated with the leg portions 1-4 and a butting face 33 associatedwith the leg "otherwise illustrated in FIGURE 2 is `nally assembled isillustrated in FIGURES 3A and 3B. In FIGURE 3A there is shown a coretype transformer :assembled from stacks `ZZA and 24A of laminations asshown in FIGURE 2 and including transformer windings tti and ft2overlying the abutting faces Zeit-36A and 28A-3era, respectively. Theexact naturey of the windings tti ard 42. :are not so important as theconsiderati-on that they do overlie the abutting faces therebysubstantially reducing the leakage iiux and confining the lines of strayiiux to the transformer configuration. The .stacks Z2 and 2t may besecured into place by any convenient bracket mean-s which will bring theabutting faces into intimate Vassociati-on. Of course, theV smoother andthe more intimate the association between the abutting faces the lessthe air gap and the less the fiux leakage.

In FGURE 3B there is shown a shell type transformer assembled fromstacks `22B and 24B an-d stacks 212C and Zit-C and @ranged to provide acommon center leg 4d and two outerl legs i3 and 49. The center leg 46has `overlying it and the abutting faces thereof a transformer winding52 and the legs 413 and/t9 have overlying them and the abutting facesthereof transformer windings 5t and 56. The manner of mounting isoptional, it being important only that the stacks be arranged to providea substantially gapless and intimate mating between abutting faces.

lFIGURE 4A illustrates the procedural steps that take place -in`stamping the laminations iti frorna strip of magnetically permeablematerial Sti. In this particular arrangement and in keeping with thedefinition set forth relative to FTGURE 1, the strip of material isselected to be of a width 4b. It is fed into a punch press provide-dwith two simultaneous punching operations at consecutive punchingstations. Thus, at the first stamping station, as illustrated in FIGURE4A, the strip 5% is operated upon to punch out the blank di)corresponding identically to the laminations i@ shown in FIGURE l.Thereafter, the punch press operates so as to shift the punched strip tostation 2 whereat the nal punching operation takes place to severV theblank 62 from the ystrip Sti and complete the punching operation. At thesame time that blank e2 is being punched at station 2 another lblank 6@is being punched at station 1. Thus, the punching operation is quick andefficient and produces blanks for laminations `without waste of anystrip material. FIGURE 4B illustrates another punching arrangement wherea strip of material Sti of a width l+a is subjected to ay singlepunching operation whereby the blank 64 is stamped out leaving as aresidual the blank 66, each of y.a configuration as shown in FIGURE 1.

A similar but more complicated punching operation is illustrated by therepresentation of FIGURE 5. Therein the selected punch press is designedto have at least four active punching stations whereby punchingoperations can be carried out simultaneously. Specifically, again astrip Sti ofl a width 4b is fed intoV the punch press, not shown, andprogresses therethrough in seven stations. At station A, guide slots 7d,'712, 74, '76, 78 vand Sti are punched into the strip, whi-ch slotsserve not only for alignment purposes during the subsequent stampingoperations but accurately position and identify the abutting faces onthe lamination product. At station B the first blank stamping operationtakes place Wherein the blank 82 is punched from the strip. At station Ca second punching operation takes place wherein the blank S4 is punchedfrom the strip and at station D a `final stamping ope-ration takes placewherein theblank l f Se is stamped from the strip leaving in additionthe blank 83.

In the stamping operation of FIGURE 5 the punch ing of the guide slotsdoes create some nominal waste ibut it doesy permit a better alignmentand does provide for a greater exactitude in the punching of thesurfaces that will form the abutting faces of the transformer corestacks. Other punching operations maybe performed such, for example, asmounting holes in the laminations, if desired, and a shaving operationon the face of the guide `slots that will form abutting faces of thetransformer core. The first operation may be comple-ted in either of thearrangements of FIGURES 4 `and 5 by the inclusion of an extrapreliminary punch* ing station. Similarly, the shaving operation m-ay beadded to the arrangement of FIGURE 5 'by including between station A andstation B :a separate shaving station.

In practice, laminations suited for use in the construction oftelevision power transformers have been stamped from strip steel of AISIgrade M27 and of a 24 or 26 gauge. Core type transformers constructed inaccordance with the scheme of the present invention are approximatelythree inches square with a one inch square central window. This physicalsize may be varied according to the permeability of the selectedmaterial and the desired power capacity of the transformer to beconstructed from the core.

From the foregoing it is clear that there has been provided herein a newand improved core construction and lamination therefor wherebyy a coretype transformer can be constructed from laminations stamped from astrip of magnetic permeable material without waste of that material andwherein, specifically, the laminations are of a modified U shape withone leg shorter than the other leg by a dimension corresponding to thewidth of the bight portion therein. Additionally, through use of suchlaminations it is possible to derive a transformer construction whereinwindings carried on opposite legs of the transformer enclose andencompass the abutting faces of the lamination stacks in a manner so asto substantially reduce ux leakage and prevent the formation of strayiux lines. rThus, there is presented not only a simple and eicientlamination and method of making the same, but there is formed atransformer which can be made of relatively inexpensive permeablematerial. The principles described herein may also be employed in largerdimensions for the purpose of making laminations for high kv-a. powertransformers. Y

Although the arrangement described herein is considered at present to bepreferred, it is understoodthat it merely exemplary of the principles ofthe invention and that variations and modifications may be made therein.It is intended to cover in the appended claims all such variations andmodifications as fall within the true spirit and scope of the invention.

We claim:

1. A core type transformer which comprises a first stack of laminationsincluding a first leg portion, a second leg portion and a bight portionjoining said iirst and second leg portions; said first leg portion ofsaid stack being longer than said second leg portion by an amountcorresponding substantially to the width of said bight portion; saidlaminations of said first stack being joined so that the free ends ofsaid'stacked first and second leg portions define a planar mating face;a second stack of laminations including first leg portion, a second legportion and a bight portion joining said leg portions and constructed soas to complement the coniiguration of said firstl stack of laminations;said laminations of said second stack being joined so that the free endsof said stacked first and second leg portions define a planar matingface that complements the mating face dened by the free ends of saidstacked leg portions of said first stack of laminations; Said matingfaces of said iirst and second leg portions of said respective stacksbeing intimately abutted so that a substantially rectangular coreconfiguration is defined by said abutted stacks; and first and secondtransformer windings overlying and encompassing respective ones of saidabutted mating faces and adjacent segments of said stacked leg portionsso as to minimize leakage flux and conne lines of stray flux to saidcore type transformer during the operation thereof.

2. A shell type transformer which comprises `a first stack oflaminations including a first leg portion, a second leg portion and abight portion joining said first and second leg portions; said lirst legportion of said stack being longer than said second leg portion by anamount corresponding substantially to the Width of said bight portion;said laminations of said first stack being joined so that the free endsof said stacked rst and second leg portions define a planar mating face;-a second stack of laminations including a first leg portion, a secondleg portion and a bight portion joining said leg portions andconstructed so as to complement the configuration of said first stack oflaminations; said laminations of said second stack being joined so thatthe free ends of said stacked first and second leg portions define aplanar mating face that complements the mating face defined by the freeends of said stacked leg portions of said first stack of laminations;said mating faces of said first and second leg portions of saidrespective stacks being intimately abuttcd so that a substantiallyrectangular core configuration is defined by said abutted stacks; thirdand fourth stacks of laminations constructed and abutted so as tocomplement the abutted configuration of said iirst and second stacks;said third and fourth stacks of lamii nations being joined to said firstand second stacks so as to provide a rectangular transformerconfiguration having a center leg of greater width than the two end legsthereof and having the planar mating faces of said leg portions of saidfirst and second abutted stacks that define a portion of saidtransformer center leg offset from the planar mating faces of said legportions of said third and fourth stacks that define the remainingportion of said center leg of said transformer; and a plurality oftransformer windings overlying and :encompassing respective ones of saidabutted mating faces and adjacent segments of said stacked leg portionsthat define said transformer legs so as to minimize leakage iiuX andconfine lines of stray flux to said core type transformer.

References Cited by the Examiner UNITED STATES PATENTS 696,953 4/02Everest 336-217 755,766 3/04 Hall 336-212 X 1,599,842 9/26 Schneider336-217 X 1,805,534 5/31 Troy 336-216 1,834,898 12/31 Boyajian 336-2162,909,138 10/59 Lawson 13-116 2,938,150 5/60 Kniel 336-215 X 3,034,4665/62 Brandes 113-116 FOREIGN PATENTS 1,035,752 8/55 Germany.

JOHN F. BURNS, Primary Examiner.

W. A. HIRTZ, Examiner.

1. A CORE TYPE TRANSFORMER WHICH COMPRISES A FIRST STACK OF LAMINATIONSINCLUDING A FIRST LEG PORTION, A SECOND LEG PORTION AND A BIGHT PORTIONJOINING SAID FIRST AND SECOND LEG PORTIONS; SAID FIRST LEG PORTION OFSAID STACK BEING LONGER THAN SAID SECOND LEG PORTION BY AN AMOUNTCORRESPONDING SUBSTANTIALLY TO THE WIDTH OFSID BIGHT PORTION; SAIDLAMINATIONS OF SAID FIRST STACK BEING JOINED SO THAT THE FREE ENDS OFSAID STACKED FIRST AND SECOND LEG PORTIONS DEFINE A PLANAR MATING FACE;A SECOND STACK OF LAMINATIONS INCLUDING FIRST LEG PORTION, A SECOND LEGPORTION AND A BIGHT PORTION JOINING SAID LEG PORTIONS AND CONSTRUCTED SOAS TO COMPLEMENT THE CONFIGURATION OF SAID FIRST STACK OF LAMINATIONS;SAID LAMINATIONS OF SAID SECOND STACK BEING JOINED SO THAT THE FREE ENDSOF SAID STACKED FIRST AND SECOND LEG PORTIONS DEFINE A PLANAR MATINGFACE THAT COMPLEMENTS THE MATING FACE DEFINED BY THE FREE ENDS OF SAIDSTACKED LEG PORTIONS OF SAID FIRST STACK OF LAMINATIONS; SAID MATINGFACES OF SAID FIRST AND SECOND LEG PORTIONS OF SAID RESPECTIVE STACKSBEING INTIMATELY ABUTTED SO THAT A SUBSTANTIALLY RECTANGULAR CORECONFIGURATION IS DEFINED BY SAID ABUTTED STACKES; AND FIRST AND SECONDTRANSFORMER WINDINGS OVERLYING AND ENCOMPASSING RESPECTIVE ONES OF SAIDABUTTED MATING FACES AND ADJACENT SEGMENTS OF SAID STACKED LEG PORTIONSSO AS TO MINIMIZE LEAKAGE FLUX AND CONFINE LINES OF STRAY FLUX TO SAIDCORE TYPE TRANSFORMER DURING THE OPERATION THEREOF.